A touch screen is a display capable of detecting a physical stimulus or other contact with a foreign object (such as a finger or stylus) within a display area and interpreting the stimulus as input. The ability of a touch screen to receive (i.e., detect and interpret) a stimulus is typically enabled through the use of a plurality of touch-sensitive sensors. Touch-sensitive sensors are devices that respond to a stimulus and produce a signal indicative of the stimulus's magnitude, relative position, or other characteristic attributable to the stimulus. Touch-sensitive sensors may be implemented according to a variety of technologies. Popular touch-sensitive sensor implementations in the field of consumer electronics include resistive sensing, capacitive sensing, infrared sensing, optical imaging and dispersive signal technology. Other technologies exist that are also well known in the art.
Touch screens have become increasingly popular in the field of consumer electronics. Applications in which touch screen applications may be used include display interfaces of computing devices, such as notebook computers (tablets), personal data assistants (PDAs), and mobile handsets. Other popular applications in which touch screens have been incorporated include the user interfaces of bank automated telling machines, kitchen appliances, exercise equipment, satellite navigation devices and other consumer electronics.
Displays which offer touch screen functionality provide substantial benefits over traditional displays. These benefits include the ability to directly interact with the content displayed on the touch screen, rather than indirectly with a dedicated input device, such as a keyboard, keypad, mouse, or touchpad. Another benefit of a touch screen display is the ability to receive input without requiring the presence of a dedicated input device. As consumer electronic devices (particularly mobile handsets) continue to reduce in size, the inclusion of a touch screen provides a manufacturer the ability to further reduce the size of the device by eliminating the space required for an input terminal. In addition, by devoting the entirety of a device's surface area for use as a display rather than apportioning the surface area between a display area and an input terminal (e.g., keypad), the total display area may be increased, resulting in a superior user experience.
One popular implementation of a touch screen is the simulation of an input terminal. A touch screen according to this implementation displays one or more images corresponding to the individual input units of the simulated input terminal. For example, a touch screen simulating a computer keyboard may display a “soft” (virtual) keyboard in the display area. This soft keyboard may be displayed as an image of a physical keyboard. When a stimulus (e.g., finger tap) is detected over the surface of the keyboard image, the stimulus is interpreted as a user-actuation of the key corresponding to the image. Thus, tapping the image of the letter “A” in the image of a soft keyboard is interpreted as though the user typed “A” via a dedicated input terminal.
Unfortunately, mobile computing devices such as cell phones, smart phones and PDAS which use touch screens as a primary method of input may be difficult or inconvenient to use. For example, typical touch screens lack the tactile feedback provided by pressing a tangible button or key in a physical input terminal. Accordingly, users may be uncertain whether any key was actuated at all. Further complicating the issue, the reduced sizes of many mobile computing devices naturally limit the sizes of their respective touch screens. A soft keyboard or soft keypad may be implemented with constituent keys which are tightly spaced and/or inconveniently small. A user pressing a key on a soft keyboard may obscure the visibility of a substantial portion of one or more keys just with the user's fingertip. Errant key presses may also be a common user experience. Thus, in order for the user to be assured that input is being received as intended, the user is required to monitor the output field on the display to verify both that a key was entered, and more specifically, that the correct key was entered.
However, while monitoring the output field, the user may be unable to view the soft keyboard, and must therefore estimate the position of the keys to continue entering text. Novice users in particular may find difficulty in estimating the relative positions of the keys accurately. Looking at the soft keyboard interface solves this problem, but prevents the user from verifying whether a key press was registered by the touch screen, or to view which keys the user has recently pressed, until the user again views the output field. Naturally, the constant diverting of focus between the output field and the soft keyboard may cause inconvenience to the user and inefficient input entry.
One conventional solution to this problem is to provide a feature that increases the size of the image of a key when a stimulus is detected in a static location exceeding a length of time. For example, if a user's finger tip presses a key on a soft keyboard and holds the position of the finger tip over the image of the key over a threshold period of time, the image of the key is adjusted (typically, enlarged) so that the visibility of the key is less obscured to the user by the position of the user's finger.
Unfortunately, while this solution reduces the uncertainty of the identity of the key currently pressed, it does nothing to indicate the identity of the keys previously pressed, and thus does not alleviate the inefficiency caused by requiring the user to divert attention between the output field and the soft keyboard. On the contrary, since the stimulus's position must be maintained to exceed a threshold, an additional delay results each time this feature is employed. A natural result of this delay is a corresponding decrease in efficiency.